Of all the elements, potassium is found in greatest quantity in plants, especially the young, in the form of inorganic salts.

Potassium deficiency is felt more strongly on soils with high salt content of calcium and magnesium and poor aeration. External symptom of potassium deficiency is the leaf color change, that the appearance of brown spots, especially near the extremities of the leaf. This phenomenon starts at the edge of the leaf, while the ribs and surrounding areas they remain green. Leaf edges curl and the ribs seem immersed in leaf tissues. In most plants these phenomena occur first at the older lower leaves.

Plants with potassium deficiency may have lower foliar surfaces and presents a reduction of the process of photosynthesis.

When excess potassium prolongs the period of vegetation and delayed maturation. Plants developed in terms of potassium enough fade faster and more pronounced than plants supplied with potassium.